Weak Flipper - 1984 Bally

[Rando]

Hi all,
I have a weak flipper on my 1984 Bally Spy Hunter.  It's one of the upper "secondary" flippers and it moves, sometimes fine, but mostly weak limiting how well you can hit/target.  I'm not sure where to start/what to look at to get started for repair.  So far I've found the information below, but it might as well be in spanish because I don't know what's what in the description info:

Symptom : Weak flip.

Check the plunger shaft and coil stop for mushrooming. A mushroomed plunger dragging against the coil sleeve is a classic cause of a weak flipper. The plunger should slide smoothly and cleanly back and forth inside the coil. Any resistance indicates a problem.

Also, check for a worn out EOS switch, if this is a non-Fliptronic system. An EOS switch with high resistance will never cause the holding side of the coil to disengage from the circuit. This puts the coil permanently into a "holding" state, and it can't provide power, not near enough, for a strong flip.

Appreciate any help on where to start!

[ChadTower]

That is where you start.  It's either mechnically binding or the electricity isn't getting through it well. 

Pull up the playfield and look at the flipper assembly.  Get to know the parts a little bit, make it move with your fingers, and you'll start to understand the moving parts.  Then come back and read that again.  Most likely is that the plunger is the issue and you'll need to pull that out, file the end of it down a little bit, and then replace the coil sleeve.